This invention relates to a semiconductor device test probe, manufacturing method therefor and a semiconductor device tested by such the probe.
With the conventional test probe as shown in FIG. 13a, the testing (probing) is carried out by attaching a probe 202 having a for and bent into a hook-like shape to a probe card 201 which is vertically movable, and pushing the probe 202 against a test pad of a semiconductor integrated circuit (referred to as an electrode pad herein after) in such a manner than an oxide film on the pad surface is broken off to establish true contact (electrical contact) between the probe and a fresh surface of the pad. The condition of a probe tip under the probing is shown in FIG. 13b. For the sake of easy understanding, FIG. 13b is illustrated in the form of a simplified model with respect to dimensions and the like. As shown in FIG. 13b, the tip 200 of the conventional probe is originally finished to have a flat end face, so that at the time of probing the whole of the flat tip portion is brought into contact and an oxide film 204 and contaminants on the surface of the electrode pad 203 are left interposed between the probe tip and the pad surface.
Further pressing of the probe against the electrode pad to drive it by 50–100 μm further downward (overdrive) causes the inclined tip of the probe to slip and break a portion of the oxide film 204 to make the conducting portion 206 through which an electrical true contact is established, permitting the conduction test to be achieved. At this time, the probe is slightly rotated by flexure. Therefore, in a probe card having a number of probes with a flat finished tip, an angle of the flat surface at the probe tip portion is not equal to each other during the overdriving, thus posing a problem that the contact state is not stable.
Also, in Japanese Patent Laid-Open No. 6-61316, an example is disclosed in which the tip of the probe is formed into a sphere-shape or an oval sphere-shape in order not to damage the electrode pad of the integrated semiconductor device. In this example, differing from the one in which the tip portion is finished flat, any problem due to the deviation of the contacting surface areas does not arise.
Japanese Patent Laid-Open No. 8-166407 discloses an example of a probe for testing lead portions (final test) of a semiconductor device, wherein the radius of curvature r of the tip portion of the probe is made from 0.5R to 5R (R is the diameter of the tip portion of the probe), whereby the contacting area becomes more stable as compared to the case where the tip portion is flat for the reasons the same as that for the foregoing spherical tip portion, thereby to suppressing the temperature rise of the probe and preventing the welding of Sn. Here, the minimum radius of curvature is set at the machining limitation or to be a semi-sphere shape. Also, the reasons for the maximum limit of 5R is explained to be for the purpose of preventing the ridge defined between the side portions and the spherical tip portion from planing the plated Sn.
Japanese Patent Laid-Open No. 5-273237 discloses a structure for bringing the tip of the probe into a line contact with an electrode pad. According to this paper, even if the electrode pad is small, the probe does not fall off from the pad, allowing an accurate measurement, so that the tip portion may preferably have the shape as shown in FIG. 14.
Further, Japanese Patent Laid-Open No. 8-152436 discloses an example as shown in FIG. 15 in which the probe comprises a first surface 207 that becomes parallel to the pad surface when the tip of the probe is brought into contact with the semiconductor pad and a second surface 208 that is parallel to the pad surface during the test. According to this probe, the first surface 207 causes an oxide film on the electrode pad to separate to expose the surface without the oxide film, thereby to ensure the good contact state. The second surface is three times larger than the first surface, ensuring the sufficient contact surface area.
Also, since tungsten used as the probe material is made of sintered powder material, the finishing of the tip shape is often achieved by the electrolytic abrasion, but since agglutination can easily take place when the surface coarseness is large, the forgoing Japanese Patent Laid-Open No. 8-166407 proposes a measure for decreasing the surface coarseness by selecting a suitable electrolytic conditions. Also, the effectiveness of polishing the tip into a mirror surface is disclosed also in Japanese Patent Laid-Open No. 8-152436.
Since the conventional probe is constructed as above and the true contact area between the tip portion of the probe and the electrode pad at the time of test (electrically conductive portion 206) is extremely small, a sufficient conduction was some times not properly provided. Also, the repeated probing causes the oxide films 204 to build up on the tip portion 200 of the probe, the true contact surface area relative to the electrode pad is decreased, making the electrical conduction unstable.
Also, even though the stress may be decreased by making the tip portion spherical, the oxide film cannot sufficiently be removed, so that a sufficient true contact surface area cannot be maintained. That is, even when the contact surface is made large, the remains of the aluminum oxide film immediately below the spherical surface impedes the stable contacting and it is necessary to rather frequently remove the aluminum oxide that attaches to the tip portion as the number of times of contacts increase.
In the structure for achieving the separation of the oxide film and the establishment of a true electrical contact by different respective tip surfaces such as shown in FIG. 15 which is an arrangement suggested to solve the problem of residual oxide film, it was found that, while good results were obtained at the initial state, some probes generate poor contacts as the number of times of contacts increases. As a result of the observation and the analysis of the state of the probes in connection with this problem, it was found that when the second contact surface is brought into contact with the electrode pad and repeat this test several times, the second contact surface has aluminum attached thereto, which increases the contact resistance when oxidized. The above assumption is considered reasonable from the fact that this phenomenon generated more often after the exchange of the semiconductor wafer and the halt of the line, i.e., when the test is interrupted for more than several minutes. It is considered that the reason some probes generated poor contacts and some other did not is because the contact surfaces have different from angles in view of the fact that the number of probes are simultaneously brought into contact with the electrode pads, so that it is difficult in the arrangement shown in FIG. 15 to work the first and the second flat surfaces to precision and posed problem in multi-pin measurement which will be more often required in the future.
Another problem was that aluminum which is the electrode material penetrates into polishing scars generated during the probe surface polishing and this aluminum oxides to cause improper contact. It was also found that, since the tungsten probe material has cavity holes therewithin because of it being a sintered body, aluminum enters into the cavities and oxidize, leading to a poor contact.
Also, when the wire bonding is achieved to the semiconductor device after it is tested by the probes, the probe trace causes the yield of the bonding to be decreased. Particularly, when the electrode pad is made small and at the same time the bonding size is made small to make the semiconductor device small in order to increase the number of semiconductor device taken per one wafer, the size of the probe trace is desired to be small which disadvantageously affects the electrical contact, resulting in that the bonding yield was decreased.
The chief object of the present invention is to provide a new and improved semiconductor device test probe free from the above discussed problems of the conventional test prove.
An object of the present invention is to provide a semiconductor device test probe in which the true contact surface area between a probe tip portion and an electrode pad can be increased and a sufficient reliable electrical connection with a minimum probe sliding amount can be established.
Another object of the present invention is to provide a semiconductor device test probe which is maintenance free in the sense that electrode material does not stick to it.
A further object of the present invention is to provide a method for manufacturing a semiconductor device test probe for manufacturing a test probe in which the true contact surface area between a probe tip portion and an electrode pad can be increased and a sufficient reliable electrical connection with a minimum probe sliding amount can be established.
Another object of the present invention is to provide a manufacturing method for a semiconductor device test probe which is maintenance free in the sense that electrode material does not stick to it.
A still another object of the present invention is to provide a method for manufacturing a semiconductor device test probe for manufacturing a test probe in which the true contact surface area between a probe tip portion and an electrode pad can be increased and a sufficient reliable electrical connection with a minimum probe sliding amount can be established.
Another object of the present invention is to provide a reliable semiconductor device tested by the probe of the present invention.